How Patagonia Slimmed the Puffer Coat Way Down

SOMEONE WHO’D BEEN lost in the wilderness for a few years with only an old-school puffer coat to keep him warm might be surprised, upon re-entering society, to learn how much the tech jacket has changed. The bulky Michelin-Man coat has all but vanished, replaced by its comfortable, comparatively emaciated cousins. One of the sveltest newcomers yet: the Patagonia Micro Puff Hoody, which uses groundbreaking synthetic materials to combat the cold without adding to your load, leaving you clammy, or hogging more than your fair share of space in the subway.

Traditionally, designing a jacket built to perform in the field has involved trade-offs: While premium down traps heat and weighs little, it loses its ability to retain warmth when it’s wet. For their part, synthetic insulations often cost less and fight the elements more cleverly but can weigh more and bulk up a design. So big brands have forged ahead to improve both approaches: on the one hand, treating down with water-resistant nano-coatings; on the other, developing thinner, lighter synthetic insulations that stay warm without additional volume.

The result, for alpine guides like Nat Patridge, is more comfort in the wild. “Synthetics have become more functional, with an emphasis on lightness,” said Mr. Patridge, who owns Exum Mountain Guides in Jackson, Wyoming. “Over 25 years, my pack has gotten lighter while my comfort level has gotten so much better.”

With its new jacket, Patagonia went the synthetic route, using PlumaFill, an innovative insulation whose ultrathin filaments create pockets of air that capture warmth. Its brick-quilted outer layer of specialized ripstop nylon blocks the wind but allows excess heat and moisture to pass through. When you’re done wearing it, the jacket packs down into a small pouch or (rather miraculously) its own pocket—more squishable than many other synthetic-filled coats.

To reduce surprising cold spots often found in puffer coats, the baffling is stitched discontinuously to allow heat to flow throughout the body, while fewer pieces of fabric were used to cut down weight. Patagonia’s fits can be generous compared to more sculpted European outdoor brands: The cut here lands somewhere between traditional and athletic, a little roomy if you want to layer the coat comfortably over a sweater.

The men’s version of the Micro Puff Hoody weighs about nine ounces, the women’s just eight ounces—light enough that your mind barely registers that you’re wearing it. It’s the rare jacket suited for both a climb to the frigid top of Mount Katahdin, or the more hospitable top of the high school’s football bleachers. Jacket, $299; patagonia.com